Chloe Zhang
With the world moving towards sustainability, there is a growing need to find eco-friendly alternatives to conventional plastics. One such alternative that has gained popularity is polylactic acid (PLA), a plastic substitute made from fermented plant starch, usually corn. While PLA is biodegradable, carbon-neutral, and does not emit toxic fumes when incinerated, there are several concerns about its sustainability. Firstly, the cultivation of corn for PLA requires more nitrogen fertilizer, herbicides, and insecticides, contributing to soil erosion and water pollution. Secondly, PLA has a slow biodegradation rate and requires separate recycling from conventional plastics. Additionally, there are limited industrial-grade composting facilities capable of handling PLA disposal. Furthermore, the production of PLA may involve the use of genetically modified corn, and the process generates more pollutants than traditional plastic production. Despite these challenges, PLA offers a promising start in the search for sustainable alternatives to conventional plastics.
| Characteristics | Values |
|---|---|
| Eco-friendly | PLA is eco-friendly, but it has a slow rate of biodegradability, requires more land use, and contributes to ozone depletion. |
| Biodegradable | PLA is biodegradable, but it requires a "controlled composting environment" to break down within 90 days. |
| Recyclable | PLA cannot be recycled with other plastics and must be kept separate. |
| Carbon neutral | PLA is carbon neutral, but it is made from genetically modified corn, which has unknown future costs to the environment and human health. |
| Cost | PLA is 20-50% more costly than comparable materials, but prices are decreasing as production methods improve. |
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What You'll Learn
PLA is carbon neutral but has a slow biodegradation rate
Polylactic acid (PLA), a carbon-neutral plastic substitute made from fermented plant starch (usually corn), is becoming a popular alternative to traditional petroleum-based plastics. PLA is technically carbon neutral because it is made from renewable, carbon-absorbing plants, which can help reduce emissions of greenhouse gases.
However, one of the drawbacks of PLA is its slow biodegradation rate. While PLA is compostable, it requires a "controlled composting environment" to break down effectively. This means that it needs to be processed in an industrial composting facility heated to 140 degrees Fahrenheit and fed a steady diet of digestive microbes. In these conditions, PLA can break down into carbon dioxide and water within three months. However, most consumers do not have access to such composting facilities, and PLA will take significantly longer to decompose in a home compost bin or a landfill.
The slow biodegradation rate of PLA is a significant concern, especially considering the limited number of industrial-grade composting facilities. As a result, PLA may end up in landfills, contributing to pollution levels despite being biodegradable. Therefore, while PLA is carbon neutral, its slow biodegradation rate poses challenges to its sustainability and effectiveness as a replacement for traditional plastics.
To address the slow biodegradation rate of PLA, improvements in the disposal and reprocessing methods are necessary. Additionally, consumers can play a role by opting for reusable containers, such as cloth bags, baskets, and backpacks, instead of disposable PLA products. While PLA has potential as an eco-friendly alternative, fully realizing its benefits requires addressing the challenges related to its biodegradation process.
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PLA is compostable but not recyclable
Polylactic acid (PLA), a popular alternative to traditional petroleum-based plastics, is made from fermented plant starch, usually corn. While it is compostable, it is not recyclable.
PLA is technically carbon neutral as it is made from renewable, carbon-absorbing plants, which can help reduce emissions of greenhouse gases. It also does not emit toxic fumes when incinerated. However, the corn used to make PLA is often genetically modified, which has unknown future costs to the environment and human health. The cultivation of corn also uses more nitrogen fertilizer, herbicides, and insecticides than any other US crop, contributing to soil erosion and water pollution.
The biggest problem with PLA is that it requires very specific conditions to be properly composted. Instead of being recycled with regular plastic, it needs to be sorted separately and brought to a "closed composting environment", or it will contaminate the recycling stream. When sent to industrial composting facilities, PLA must be heated to 140 degrees Fahrenheit and exposed to digestive microbes that can biodegrade it. These conditions are not typically met in backyard compost bins or landfills, meaning that PLA often does not break down as marketed.
There are also very few industrial-grade composting facilities that can handle PLA. In the US, there are only 113 such facilities, and only about a quarter of them accept residential food scraps. This puts pressure on consumers to ensure their PLA waste is being sent to the right facility, which is often impractical.
Overall, while PLA is compostable, it is not recyclable and has several environmental issues that must be addressed before it can be considered a truly sustainable alternative to traditional plastics.
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PLA is made from genetically modified corn
Polylactic acid (PLA) is a popular alternative to traditional petroleum-based plastics. It is made from fermented plant starch, usually corn. PLA is carbon-neutral, does not emit toxic fumes when incinerated, and is biodegradable. However, it has a slow rate of biodegradability and cannot be mixed with other plastics in recycling.
PLA is typically made from genetically modified corn, especially in the United States, where NatureWorks, a subsidiary of Cargill, is the largest producer of PLA. Cargill is the world's largest provider of genetically modified corn seed. With the increasing demand for corn to make ethanol fuel and PLA, companies like Cargill have been tampering with genes to produce higher yields.
The use of genetically modified corn to produce PLA is controversial. While it provides a good reason to alter crop yields with genetic splicing, the future costs of genetic modification to the environment and human health are still largely unknown and could be very high. Environmentalists argue that the cultivation of corn uses more nitrogen fertilizer, herbicides, and insecticides than any other U.S. crop, contributing to soil erosion and water pollution.
NatureWorks acknowledges these criticisms and points out that the corn it uses is low-grade animal feed not intended for human consumption. They also process a small amount of non-genetically engineered corn for specific customers. Additionally, NatureWorks is investigating better ways to segregate PLA in traditional recycling facilities and is investing in renewable energy certificates to offset its use of fossil fuels.
Overall, while PLA made from genetically modified corn has advantages as a biodegradable and carbon-neutral alternative to traditional plastics, there are concerns about the environmental and health impacts of genetic modification that need to be carefully considered.
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Corn cultivation has a steep environmental toll
The environmental impact of corn cultivation is further exacerbated by the extensive land use required for bioplastics production. It is projected that to meet the growing global demand for bioplastics, more than 3.4 million acres of land—an area larger than Belgium, the Netherlands, and Denmark combined—will be needed. This large-scale land use can contribute to habitat destruction and fragmentation, affecting biodiversity and ecosystem health.
In addition, the use of genetically modified corn in the production of polylactic acid (PLA) corn plastic is a cause for concern. While genetic modification can lead to higher crop yields, the future costs to the environment and human health are still largely unknown and could be significant. The potential risks associated with the release of genetically modified organisms into the environment, including the potential impact on non-target species and the development of herbicide-resistant weeds, are important considerations in the discussion of corn-based plastics' sustainability.
Furthermore, the biodegradability of PLA corn plastic is slower than initially believed. While PLA does biodegrade, it requires specific conditions, such as a "controlled composting environment" with high temperatures and the presence of digestive microbes. Without access to industrial composting facilities, the breakdown process can take significantly longer, potentially negating the environmental benefits of using biodegradable materials.
While corn-based plastics offer a promising alternative to traditional petroleum-based plastics, it is essential to recognise that corn cultivation and the production of bioplastics have their own environmental challenges. To fully assess the sustainability of corn-based plastics, it is necessary to consider the life cycle impact, including the environmental costs associated with corn cultivation and the end-of-life disposal of PLA materials.
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PLA is more expensive than traditional plastics
Polylactic acid (PLA), a plastic substitute made from fermented plant starch (usually corn), is a popular alternative to traditional petroleum-based plastics. PLA is technically carbon neutral, as it comes from renewable, carbon-absorbing plants, and does not emit toxic fumes when incinerated. However, one of the major concerns that people have about bioplastic is how they hold up against their petrochemical competitors.
Bio-based polymers tend to not be as strong as fossil fuel-based polymers, although they often don't need to be. PLA is most frequently used as an alternative to non-bio plastics in low-stress applications like cups, food packaging, and bags, where it is strong enough for single-use. PLA is also more expensive than traditional plastics due to the number of steps required in the production process. As PLA becomes more widely available, the efficiencies of scale come into play, which means the cost may decrease.
The environmental and economic advantages of PLA bioplastics over conventional plastics are measurable and significant. PLA is a polyester (polymer containing the ester group) made with two possible monomers or 'building blocks': lactic acid and lactide. Lactic acid can be produced by the bacterial fermentation of a carbohydrate source under controlled conditions. In this case, the carbohydrate source can be corn starch, cassava roots, or sugarcane, making the process sustainable and renewable on an industrial scale.
In addition to using the agricultural produce itself, crop residue like stems, straw, husks, and leaves can be processed and used as alternative carbohydrate sources. This means that agricultural by-products that would have otherwise been thrown away can be utilized. However, it is important to note that the recycling infrastructure for PLA hasn't been scaled up yet, mainly because end markets for the recycled material haven't been developed. Therefore, recycling PLA might be a viable solution in the future, but not currently.
Today, composting is the preferred end-of-life option, especially as food service packaging is often contaminated with food scraps, making recycling impractical. However, the types of facilities required for successful biodegradation are in short supply, meaning more PLA ends up in landfills or the environment instead of being recycled or decomposed. While PLA does biodegrade, it does so very slowly. According to Elizabeth Royte, PLA may break down into its constituent parts (carbon dioxide and water) within three months in a "controlled composting environment," an industrial composting facility heated to 140 degrees Fahrenheit and fed a steady diet of digestive microbes.
It is also worth noting that the cultivation of corn uses more nitrogen fertilizer, herbicides, and insecticides than any other US crop, contributing to soil erosion and water pollution when nitrogen runs off fields into streams and rivers. With the increasing demand for corn to make ethanol fuel, it is no wonder that companies have been tampering with genes to produce higher yields. However, the future costs to the environment and human health of genetic modification are still largely unknown and could be very high.
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Frequently asked questions
Polylactic acid (PLA), or corn plastic, is a plastic substitute made from fermented plant starch, usually corn.
Corn plastic is more sustainable in some ways, but less in others. It is technically carbon neutral, as it comes from renewable, carbon-absorbing plants, and it does not emit carbon dioxide when it breaks down. However, more pollutants are produced when making corn plastic compared to traditional plastic, due to the fertilizers and pesticides used in growing the corn.
Yes, corn plastic is biodegradable, but it takes a long time. In a "controlled composting environment," which is an industrial composting facility heated to 140 degrees Fahrenheit, PLA will break down into carbon dioxide and water within three months. However, in a compost bin or landfill, the process will take much longer.
No, corn plastic cannot be recycled. It must be kept separate from other plastics when recycled, or it will contaminate the recycling stream. Instead, it needs to go to a composting facility, but there are currently very few of these facilities available to consumers.
Consumers can use reusable containers, such as cloth bags, baskets, and backpacks, instead of disposable corn plastic.
